A near spurious-free 6 GHz laterally-excited bulk acoustic resonator with single-sided wavy electrodes

Abstract Laterally excited bulk wave resonators demonstrate outstanding electromechanical coupling coefficient ( K eff 2 ) suitable for the design of wideband filters. However, it has not been commercialized due to the spurious modes and low temperature coefficient of frequency (TCF). In this paper, a near spurious-free 6 GHz resonator (SW-BAR) is proposed with single-sided wavy edges in the aperture direction. The SW-BAR suppress high-order harmonics in the area of the electrodes by confining the formation of standing waves. The design is fabricated using a 316 nm Z-cut lithium niobate thin film with an 18 μ m pitch ( P ). Measurements of the fabricated devices feature the spurious-free A1 mode with a high resonance frequency ( f s ) of 5.932 GHz, K eff 2 of 22.19%, and Bode_ Q max of 283. In addition, the TCF of the proposed structure has improved from −73.58 to −57.36 ppm °C −1 since the suppression of high-order harmonics at f s . The near spurious-free SW-BAR shows fascinating prospects for high-performance RF filters in 5G/6G communication.